smartctl没有从cron工作

Question

I have a problem with smartctl

Have updated from version 5.4 to the lastest version 6.4.. No change.. Same issue

It works fine when running the command smartctl -H /dev/sda directly from the command line

But when running the command from a cronjob its not working as it should. Here you can see the cron job settings.. Its running as root

The job is running every 60 sec while testing and the command doesn't return anything. Only the timestamp is written to the file.

But if I press the button "Run now" then the command works?! Very strange!? In the code you can see that the output is written to a file.. The output is empty

Another thing.. When the job is automated only one timestamp is written to the file.. Two timestamps should be written?

function check_dev($dev){
    $status_ok = "=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED";

    $output = shell_exec('smartctl -H '.$dev);

    file_put_contents('/var/www/hdd_out.txt', gmdate("M d Y H:i:s", time())."
".$output, FILE_APPEND);

    if(strpos($output, $status_ok) !== false){
        echo "$dev OK!
";

        return true;
    }
    else{
        echo "$dev ERROR!
";

        return false;
    }   
}

if(check_dev('/dev/sda') && check_dev('/dev/sdb')){
    $status = 0;
}
else{
    $status = 1;
}

output file

Jun 17 2015 10:17:01
Jun 17 2015 10:18:01
Jun 17 2015 10:19:01
Jun 17 2015 10:20:01
Jun 17 2015 10:21:01
Jun 17 2015 10:22:01
Jun 17 2015 10:23:01
Jun 17 2015 10:24:01
Jun 17 2015 10:25:01
Jun 17 2015 10:26:01
Jun 17 2015 10:27:01
Jun 17 2015 10:28:01
Jun 17 2015 10:29:01
Jun 17 2015 10:29:54 # here I manually pressed "Run now"
smartctl 6.4 2014-09-29 r3990 [x86_64-linux-2.6.32-5-amd64] (local build)
Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

Jun 17 2015 10:29:54 # here I manually pressed "Run now"
smartctl 6.4 2014-09-29 r3990 [x86_64-linux-2.6.32-5-amd64] (local build)
Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

Jun 17 2015 10:30:01
Jun 17 2015 10:31:01
Jun 17 2015 10:32:01
Jun 17 2015 10:33:01

Answer 1

The user and environment under which cron runs is often much more limited than the environment you're used to when logged into a TTY. In particular, the $PATH environment variable may be different or even empty.

It is therefore recommended to use the full path to any executable you call in the script. Since the cron script is running, the php executable is being found in the cron task itself, but the smartctl may not be found inside the PHP script.

Locate the full path to smartctl using which smartctl, then modify the PHP script to use the full path. It is likely /usr/bin/smartctl or /usr/sbin/smartctl.

Using shell_exec() makes it difficult to retrieve error information from commands called. Instead, using exec() and specifying the 3rd argument $return_var to capture the return code, along with the $output array may be more helpful.